Various types of side-release type buckles have been proposed. A typical one of such conventional buckles, described with reference to FIGS. 1 and 2, is comprised of a female member consisting of a flat cylindrical portion 101 and, a male member provided with a pair of engaging bars 102 which in a compressed state are inserted into the female member. The cylindrical portion 101 of the female member has a pair of laterally recessed sidewall portions having through-openings 103 provided in symmetrical opposition upon each side thereof, with an edge 104 of each opening 103 forming an engaging edge. Also, generally the female member is provided with a fixing slit 105 for a belt or the like at the end opposite to the end within which the male member is inserted. Also, an inner surface of the cylindrical member 101 is further provided with a guide groove 107 for mated engagement with a guide bar 106 of the male member.
The male member is provided with a pair of engaging bars 102 that extend integrally from a frame 108, one on each side of the guide bare 106. A fastening strip 109 such as a belt or the like is secured upon the frame 108 by means of an angled slit 110. Each of the engaging bars 102 has a hook portion 111 on the outer mutually opposed sides, and a barb 111a formed upon the bases side of the hook portion 111 that engages with the edge 104 of each of the openings 103 of the female member.
In the exemplary conventional buckle, the engaging bars 102 of the male member are brought slightly inwardly toward each other so as to press them into the interior of the female cylindrical portion 101, the elastic deformation of the bars 102 permitting insertion of the same into the female member so that the hook portions 111 can subsequently protrude outwardly from the openings 103 whereby the barbs 111a of the hook portions 111 engage the edges 104, binding the two members together.
In the conventional buckle, in order to disengage the members the cylindrical member 101 is gripped with one hand while the other hand is used to squeeze the hook portions 111 of the engaging bars 102 laterally inwardly toward the inner part of the cylindrical portion 101 so the barbs 111a of the hook portions 111 disengage from the edges 104 of the openings 103.
As a result, the unbuckling operation requires the use of both hands, and in addition it is necessary to push the hook portions 111 in the direction in which the male member is withdrawn from the female member at the same time that the hook portions 111 are being pushed laterally inwardly toward the inside of the cylindrical portion 101, making the unbuckling operation complex and difficult. Such a buckle is therefore not suitable for operation by young children and is also unsuitable for use as a buckle that may require emergency unbuckling.
In particular, there have been drawbacks such as when a male-female buckle is simply engaged and the male-female parts are not subjected to tension in mutually separating directions, there is required in addition to the buckling disengagement operation a further male-female separation-direction operation. Still further, in the instance where the male-female buckle members are being subjected to oppositely directed pulling forces or tension, the barbs 111a of the hook portions 111 are strongly engaged with the edges 104 of the openings 103, making it difficult to press the hook portions 111 laterally inwardly toward the inside of the female member and through the opoenings 103.